GTB Faults: Advice appreciated =)

[Guest]

Afternoon all =)

I'm currently attempting to diagnose a couple of faults in my Legacy:

- 1997 GTB manual with EJ20R motor, orange MAF, 4G 3-plug ECU,

stock standard apart from boost gauge, atmo BOV and new exhaust from down-pipes back (Primary cat still there, rear one removed.), has new fuel pump, fuel filter and K&N Panel filter.

* MAF receiving battery voltage as opposed to 5v.

* Backfiring through intake manifold on occasion (under acceleration).

* Rough idle, hesitation, when setting off at lights for example.

* Exceptionally poor fuel economy (even for a TT).

* Intermittent complete lack of boost, mainly after a brief period of boost+WOT, sometimes the boost gauge reads 0, sometimes it reaches a full-on 3psi! Ha. This lasts for up to 5 seconds, then begins to boost normally again. When this occurs I note the exhaust sounds different, as though the exhaust gate to the secondary is being held open.

* Noted when boosting it up the hill out of Mosgiel the following: Boost crept up to 20psi, engine began detting (obviously this is going to happen at that level of boost when everything is stock ha) and blowing clouds of dark grey/black smoke until I backed off.

* Primary boost is 16psi, secondary is 18psi normally (so I have observed since fitting the gauge).

Other than that, the car runs like a dream ha. =)

Your thoughts on this?

Also if anyone has an ECU for this particular model that I could borrow for half-hour or so, I'd be grateful. =)

Cheers good people!

-Si

[legacy666]

check engine codes?

[Guest]

Ooops! I forgot to say: No codes present. =)

[gazzy2000]

frig! that boost sounds waay to hight mate, some one must of been mucking around with it?

[Guest]

Hehe. =) Not that I've seen so far. I've done a considerable amount of research on Google and have come to the conclusion that the boost is meant to be 10-11psi primary and 12-14psi secondary, this sound about right? I'm wondering if the ECU is a a bit crook and sending odd voltages, and not correctly dutying the boost solenoids...

[gazzy2000]

 MadSi said:

Hehe. =) Not that I've seen so far. I've done a considerable amount of research on Google and have come to the conclusion that the boost is meant to be 10-11psi primary and 12-14psi secondary, this sound about right? I'm wondering if the ECU is a a bit crook and sending odd voltages, and not correctly dutying the boost solenoids...

yea that PSI sounds about right, getting upwards of 20PSI would dam near blow those little turbo to bits lol, not to mention your engine!

i wudnt suspect the ECU at this stage, i hate to even speculate what the issue is on those Twin Turbos, they are a whore lol, some one on here will hook you up with the advice you need.

[gazzy2000]

 gazzy2000']

[quote name='MadSi said:

Hehe. =) Not that I've seen so far. I've done a considerable amount of research on Google and have come to the conclusion that the boost is meant to be 10-11psi primary and 12-14psi secondary, this sound about right? I'm wondering if the ECU is a a bit crook and sending odd voltages, and not correctly dutying the boost solenoids...

/quote]

yea that PSI sounds about right, getting upwards of 20PSI would dam near blow those little turbo to bits lol, not to mention your engine!

i wudnt suspect the ECU at this stage, i hate to even speculate what the issue is on those Twin Turbos, they are a whore lol, some one on here will hook you up with the advice you need.

Oh and if the ECU wastnt duting the boost noids it wud run wastegate pressure, i.e. 5-9 PSI +/-

[Guest]

20 sounds like free boost.any leaks or missing vacume hoses on your turbo's?

[Guest]

All hoses accounted for and appear to be leak-free.

Any thoughts on the voltage at MAF? I was under the impression it should be a 5v feed, but it's getting battery voltage heheh. =)

[Joker]

4G? are you sure?

[Guest]

Completely sure, I've sighted the ECU myself. =)

4G, 22611 AC561, A18-000 DH9 are all the numbers off it. =)

[Guest]

not too sure about the maf situation.or the ecu cant help you out there,

[Joker]

http://homepages.ihug.co.nz/~ccgrant/leggymodels.htm

ok so 4G is correct, sorry I have a 98 with a 87 ECU which threw me off

link at the bottom for more cool stuff Legacy specific

atmo bov is my suspect - I am lucky to get 350 km from a tank.. need to find a bung for mine and see if it makes a difference (50/50 currently), other than that cant really help too much

[gtb36]

 MadSi said:

Afternoon all =)

I'm currently attempting to diagnose a couple of faults in my Legacy:

- 1997 GTB manual with EJ20R motor, orange MAF, 4G 3-plug ECU,

stock standard apart from boost gauge, atmo BOV and new exhaust from down-pipes back (Primary cat still there, rear one removed.), has new fuel pump, fuel filter and K&N Panel filter.

* MAF receiving battery voltage as opposed to 5v.

* Backfiring through intake manifold on occasion (under acceleration).

* Rough idle, hesitation, when setting off at lights for example.

* Exceptionally poor fuel economy (even for a TT).

* Intermittent complete lack of boost, mainly after a brief period of boost+WOT, sometimes the boost gauge reads 0, sometimes it reaches a full-on 3psi! Ha. This lasts for up to 5 seconds, then begins to boost normally again. When this occurs I note the exhaust sounds different, as though the exhaust gate to the secondary is being held open.

* Noted when boosting it up the hill out of Mosgiel the following: Boost crept up to 20psi, engine began detting (obviously this is going to happen at that level of boost when everything is stock ha) and blowing clouds of dark grey/black smoke until I backed off.

* Primary boost is 16psi, secondary is 18psi normally (so I have observed since fitting the gauge).

Other than that, the car runs like a dream ha. =)

Your thoughts on this?

Also if anyone has an ECU for this particular model that I could borrow for half-hour or so, I'd be grateful. =)

Cheers good people!

-Si

pm me i have a good one 4G 3-plug ECU

[Guest]

Thanks gtb36, PM sent. =)

[gtb36]

 MadSi said:

Thanks gtb36, PM sent. =)

iam sorry its a t4 3-plug ECU for a 96 gtb